Unboilable bug points to hotter origin of life

Friday 15 August 2003 04.14 EDT
First published on Friday 15 August 2003 04.14 EDT

Scientists have discovered the world's toughest life form. The single-celled microbe, called "strain 121" for the moment, can survive at a scorching 130C higher than the boiling point of water and nearly 20 degrees higher than the previous record holder.

The discovery is announced today in the journal Science by Derek Lovley and Kazem Kashefi of the University of Massachusetts at Amherst. It raises the possibility that life began on earth earlier than currently thought.

"Our goal was not to break the temperature limit," said Prof Lovley. "As part of the general characterisation of any organism, you look at what temperature range it can survive.

"With this organism we kept ratcheting up the temperature and it just kept surviving until, basically in desperation we put it in an autoclave, which is supposed to kill all living organisms."

After 10 hours at 121C strain 121 was still alive and well. Prof Lovley said it took a temperature of 130C to finally kill the microbe.

The previous record holder for temperature endurance is a microbe called pyrolobus fumarii, which can survive up to 113 degrees celsius.

Strain 121 was collected by the research team in the Juan de Fuca ridge, which separates tectonic plates in the Pacific, 2,400 metres (a mile and a half) deep, which regularly vents iron and sulphur compounds.

Prof Lovley became interested in organisms living at high temperatures when he noticed large amounts of magnetites - rocks containing large amounts of iron - turning up in unusual environments, such as deep in the earth's crust.

Magnetites are produced where "iron-breathing" micro-organisms exist, and they are therefore good evidence of the presence of life.

Prof Lovley said: "As you go deeper in the earth it gets hotter, so as you increase the known temperature limit for life, this increases the depth at which you might find life."

It also means that life may have begun when the planet was hotter, and therefore older, than previously thought.